The present invention relates generally to the field of rehabilitative conduit liners and specifically to a method for sealing gaps or annular spaces, such as those which commonly exist at the connections between service, or lateral, line openings and rehabilitative conduit liners, using a sprayed-on, cured-in-place annulus seal. Such liners are commonly used to reduce the infiltration and inflow of extraneous ground water into sewer collection systems and the release of untreated waste into the environment. However, even with the use of such liners, there often remains an annular space between the liner and pipe, which space may provide for the entry of groundwater into, or the loss of sewer contents from, the liner at locations such as service line ports or at liner section ends (which are commonly located at manholes).
The technology of rehabilitative conduit or pipe lining is widely varied and well known in the prior art and in practice and is only described generally herein. Through relining, sewer lines may be rehabilitated without the need for expensive and labor-intensive subterranean digging, trench support installation, and the accompanying risk to workers. In general, relining is accomplished by inserting an uncured and typically cuffed liner into a length of existing sewer conduit, everting the cuffed liner through application of mechanical, hydraulic, or other force, and allowing the liner, or a coating on the liner, to cure in place. In this manner, the inserted liner becomes a rigid and continuous pipe-within-a-pipe. Typical liner inserts include resin-impregnated felt liners (or other resin-impregnated porous material), folded or flattened PVC or polyethylene pipes, or other materials. Commonly known processes include the Insituform(trademark) cured in place pipe relining process. Because the new lining is continuous, openings must be cut in the liner shortly after installation to return sewer service to connecting lines (service lines, lateral lines, or any other connecting lines) or to existing homes or facilities whose service line connections may be covered by the newly installed liner.
The installation process for most prior art liners includes heating to effect curing of the liner during installation and subsequent cooling of the cured liner to an ambient temperature determined by the surrounding earth and the contents of the pipe. During the heating process, liners are cured and/or pressurized to mold to the interior of the host pipeline. Once the liner has cured, a minute annulus may be created due to the shrinking of the heated liner during cooling or due to conduit surface irregularities. This annulus may create a pathway for the migration of inflowing and infiltrating groundwater to enter the collection system from the exterior of the newly installed liner. In particular, this pathway allows for the entry of migrating fluid into the liner at ports such as lateral openings or at other locations where the liner is not continuous. These same locations may serve as points where sewage or waste may migrate from the system.
Typically, the points of entry include not only the lateral or house service line connections or ports, but also the beginning and ending of pipe liner sections at locations such as manholes. All intersecting or joining pipes or conduits are referred to herein generally as lateral lines. At the manholes, the annular space may be easily accessible for a post-liner-installation annulus sealing, as illustrated in U.S. Pat. No. 5,879,501 issued Mar. 9, 1999 to Livingston. However, for remote lateral connections, the annulus is hidden by virtue of its location and by virtue of the newly installed liner, and the lateral connection is not readily accessible. When the liner is cut at the ports at these remote locations to return service to the lateral lines, migrating waste or water may move between the newly lined pipe and the annular space.
The known technology for returning service to existing lateral lines employs a remotely controlled sled which may be driven or pulled through a lined pipe and which includes a cutting arm. The cutting arm is longitudinally retractable from a typically cylindrical body and has on its end a rotary cutting blade or bit that may be used to open ports by cutting through the liner at the points of lateral connections. Because service must quickly be returned to the sealed lateral line connections to prevent the back-up of sewage or waste through lateral lines, the cutting often must occur before the recently installed liner is completely cured. The uncured liner, when exposed to the violence of the cutting process, tends to shower uncured resin about the area of cutting. This uncured resin, along with other debris, may pollute remote sensing equipment. Because the resin may become impossible or unduly burdensome to remove without causing damage to the sensors if allowed to cure after arriving on a lens, light or sensor, workers must frequently withdraw the sensors from the confined space to a location, such as a manhole, where they may manually clear the sensor of resin and dirt. Then, workers must relocate the lateral service connection and continue the cutting operation. The process of repeated withdrawal, cleaning, and relocation dramatically increases the time and labor costs associated with pipe rehabilitation.
Similarly, prior methods for sealing the annular space between the liner and the conduit at lateral connections have required exorbitant, expensive and time-consuming labor and repeated insertion and withdrawal of equipment or liner elements. Therefore, in addition to the labor expended to perform the cleaning and periodic repair that is required in association with the use of traditional cutters, labor and time must be expended in yet a further step in the process of sewer rehabilitation. In the field of sewer maintenance, where the investment of employee time, vehicle time and equipment time in a project directly impacts project cost, and therefore profit, it is imperative to eliminate or minimize process steps to remain competitive. Therefore there has been and remains a need for a method to seal junctions between rehabilitative liners and adjoining pipes that will allow fast and convenient sealing with a minimum need for the investment of labor and time.
U.S. Pat. No. 5,879,501 discloses a method for sealing openings in sewer manholes wherein a polymeric coating is formed on the interior surface of manhole walls, and a generally tube-shaped polymeric sealing member that is coaxially aligned with the coating is formed to be integral with the coating. After these coatings and tube-shaped members are cured, a rehabilitative liner is inserted through the cured tube and coating. The rehabilitative liner is selected to have an exterior surface adapted to permanently bond with the already-cured tubular sealing member. The ""501 patent therefore teaches a sealant method for use in a manhole opening wherein an annulus sealer is sprayed and cured in place to form a hardened gasket prior to the introduction of a rehabilitative pipe liner. In fact, the ""501 patent describes the process as demanding the use and removal of forms to create the tube-shaped sealing member and optional additional steps of roughening the cured sealing member with sandpaper or other abrasive means to create a mechanical bond that will enhance the chemical bond between the later-installed liner and the previously cured sealing member.
U.S. Pat. No. 4,439,469 issued Mar. 27, 1984 to Wood discloses a method for the rehabilitative lining of sewer pipes. In the ""469 patent the process for liner installation is described generally, without reference to the sealing of resultant annular spaces. U.S. Pat. No. 5,405,218 issued Apr. 11, 1995 to Hyde-Smith discloses a method for spray-applying a fast curing rehabilitative manhole liner as a combination of a sprayed-on compound having at least two isocyanate groups and a sprayed on amine-terminated compound having at least two reactive amine groups. U.S. Pat. No. 6,068,725 discloses a post-lining sealant method wherein a resin-impregnated liner in the general shape of a top hat is placed at a lateral opening in a cured rehabilitative liner and forced into the lateral line and outward through the use of an inflatable bladder. The bladder is part of an installation device that is positioned in the rehabilitative liner at the lateral line and controlled from a remote location. Through the use of the top-hat configuration, a seal is allowed to cured on the interior of the rehabilitative liner and the interior of the lateral line to cover the connection and the annular space from the liner interior. Finally U.S. Pat. No. 4,434,115 discloses a method for lining side or lateral connection pipes. None of these prior art patents disclose a method for placing an unactivated sealant at points of future liner ports and causing the sealant to be activated to form an annulus gasket after installation of the liner through application of a curing means to the rehabilitative liner.
Therefore, there has been and remains a need for an improved method to seal the annular space that may be formed between a pipe and a rehabilitative liner inserted into the pipe. Such an improved method is needed to lessen the requirement for labor expense associated with extra process steps in addition to worker downtime as multiple layers of liner or sealer are applied, allowed to cure, and subsequently treated in anticipation of receiving a rehabilitative liner.
An annulus sealant and method employs an expandable material, such as a heat-activated urethane foam, that may be sprayed in an unactivated or at least partially un-expanded state onto lateral or side connections or manhole ports prior to pipe relining. The expanding material is activated by the means applied to cure the rehabilitative pipe liner upon installation. In this manner, the present invention allows convenient application of uncured annulus sealant to appropriate locations during an initial investigation or preparatory viewing or cleaning of the pipe to be lined. An applicator for the foam or other uncured gasket-forming material may be mounted along with the television camera or other remote sensing equipment and the foam may be applied during such an initial observation and/or cleaning step. By combining the spraying of lateral line sealant with an initial investigative step, and by combining curing of lateral line sealant with the curing of the rehabilitative pipe liner, the need for additional loading, locating, withdrawal, and insertion is minimized or eliminated. Because the expansion and curing of the sealant gasket occurs during the time coinciding with and surrounding the curing of the rehabilitative pipe liner, excess gasket-forming sealant may be liberally applied and later cut in the same process that allows cutting of the lateral line opening, i.e., the newly formed gasket may be cut along with the newly cured rehabilitative pipe liner. This method of application and curing allows for access of the expanding foam into cracks, fissures, and along the annular space that may exist due to surface irregularities or due to shrinking of the rehabilitative liner during cooling.